RadioAstron space-VLBI imaging of the jet in M87 – II. The parsec-scale structure at 4.8 GHz
Year: 2026
Type: article
Abstract: ABSTRACT We present RadioAstron observations of the M87 jet obtained on 2014 February 4–5 at 4.8 GHz ($\lambda =6.2$ cm). The correlated signals between the 10-m space antenna and ground-based radio telescopes were detected up to projected baselines of ${\sim} 3$ Earth diameters (0.65 G$\lambda$). The orientation of the jet downstream of the core shifts northward, consistent with the long-term oscillating trend reported in other studies. An elliptical body mode of the Kelvin–Helmholtz instability can create the observed helical shape of the jet. The estimated wavelength of this instability mode suggests that its origin may be related to some processes in the accretion disc. We present 1.7–4.8 GHz and 4.8–15.4 GHz spectral index maps showing flattening of the spectrum along the outer streamlines and along the jet spine. Simulations and analysis show that this spectral flattening is partially artificial and is a common systematic effect of the clean procedure of Very Long Baseline Interferometry imaging. The spectral index of the M87 jet is consistent with the optically thin emission, while its steepening can be produced by the propagation of the instability modes causing higher pressure regions near the jet boundary and in its interior.
Institutions: P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Max Planck Institute for Radio Astronomy, Aalto University, Joint Institute for VLBI ERIC, Delft University of Technology, Ulsan National Institute of Science and Technology, Pontificia Universidad Católica de Valparaíso, Texas Tech University, University of Illinois Urbana-Champaign
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,046
Funders: National Science Foundation, Australian Government, International Max Planck Research School for Environmental, Cellular and Molecular Microbiology, European Commission, Commonwealth Scientific and Industrial Research Organisation, National Research Foundation, Korea Astronomy and Space Science Institute, National Research Foundation of Korea, International Max Planck Research School for Advanced Methods in Process and Systems Engineering, State Space Corporation ROSCOSMOS, Ministry of Science and ICT, South Korea, Agencia Nacional de Investigación y Desarrollo, Russian Academy of Sciences
OpenAlex ID: W7220681293